Experts have said the temperature target is already in danger of being breached, with the U.N. weather agency saying that 2016 is on course to be the warmest since records began, overtaking last year.

While 180 countries have now signed the agreement, 55 nations - covering at least 55 percent of global emissions - need to formally ratify the treaty to put it into legal effect.

Before China, 23 nations had ratified it - including North Korea - but they collectively accounted for just 1.08 percent of global emissions, according to the U.N. Framework Convention on Climate Change.

China is responsible for just over 20 percent of global emissions while the United States covers another 17.9 percent. Russia accounts for 7.5 percent, with India pushing out 4.1 percent.

Countries that ratify the deal will have to wait for three years after it has gone into legal force before they can begin the process of withdrawing from it, according to the agreement signed in Paris last year.